First-principles analysis of mechanical, optoelectronics and piezoelectric properties in buckled honeycomb GeSe monolayer☆

Our study systematically investigates the mechanical, optoelectronics, and piezoelectric properties of the buckled honeycomb GeSe monolayer (BH-GeSe) using first-principles theory. The stability of the BH-GeSe monolayer is confirmed through phonon dispersion, thermal stability, binding energy, and elastic constant analyses. Its small Young's modulus of 31.05 N/m imparts exceptional flexibility, with an ideal stress (sigma bia) of 6.2 N/m and a high fracture strain (epsilon bia) of 0.2. The optoelectronic properties are analyzed through energy band structures and light absorption spectra. The BH-GeSe monolayer is identified as an indirect semiconductor with a energy band gap of 2.95 eV at equilibrium. Biaxial strain induces notable changes in the conduction band minimum (CBM), valence band maximum (VBM), and an energy band gap. Specifically, the energy band gap decreases by up to 51 % under strain. Light absorption coefficients and energy-loss spectra are significantly enhanced, particularly in the infrared and ultraviolet regions, showcasing its superior optical properties. Piezoelectric coefficients are derived from polarization variations in clamped-ion and relaxed-ion states. The piezoelectric coefficients d11 and d31 are calculated as 11.85 pm/V and -0.71 pm/V, respectively, indicating a robust piezoelectric response that surpasses many well-studied two-dimensional materials. These results highlight the BH-GeSe monolayer as a promising material for next-generation optoelectronic and piezoelectric devices. Outstanding flexibility, straintunable electronic properties, and strong piezoelectric response position the BH-GeSe monolayer as a leading candidate for diverse applications in advanced material science.